The present invention relates to a fuel injector and to an internal combustion engine having a fuel injector. More particularly, the invention relates to a fuel injector capable of producing a fuel spray having a superior ignitability and a superior combustibility for use in an internal combustion engine having a fuel injector.
The present invention relates to a fuel injector for forming a complex fuel spray having a superior ignitability and a superior combustibility for use in an internal combustion engine.
An inlet pipe fuel injection device is a device which causes fuel to be injected into an inlet pipe of an internal combustion engine. In addition to an inlet pipe fuel injection device, there is also a direct fuel injection device, which operates to inject fuel directly into a combustion chamber (a cylinder) of the internal combustion engine. Such a direct fuel injection device is 5-33,739. disclosed in, for example, Japanese patent laid-open publication No. Hei
As disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, it is difficult to homogeneously mix fuel which has been injected directly into the combustion chamber with the air being drawn in the combustion chamber. Therefore, it is important to promote the atomizing of the fuel which has been injected directly into the combustion chamber.
To atomize the fuel, up to now, a swirling force has been imparted to the fuel which is injected from a fuel injector. As shown in the above stated Japanese patent laid-open publication No. Hei-5 33,739, a direct fuel injection device having a means for imparting a swirling force to the fuel is disclosed.
Herein, the direct fuel injection device disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, comprises an injection nozzle for injecting fuel from an injection hole, a cylindrical cover having a bottom portion constituting an air chamber at an outer side of the injection nozzle, a swirl chamber which is formed at a side of the bottom portion of the cover so as to communicate with the injection hole of the injection nozzle, and a check valve body which opens and closes the injection hole.
With the above stated conventional direct fuel injection device structure, the swirl chamber has an injection hole and this injection hole introduces air from a tangential direction along an inner peripheral face of the swirl chamber from the air chamber which is constituted in the cylindrical-shaped cover having the bottom portion. In accordance with the above stated air which is injected from the injection hole of the swirl chamber, the fuel injected through the injection hole of the injection nozzle will have a swirl force imparted thereto.
Further, the injection hole and a passage for introducing air from the air chamber into the swirl chamber are provided with a two-stage structure, namely the injection hole and the passage of the swirl chamber are provided at an upper direction and a lower direction (an axial direction of the check valve body) or an upstream side and at a downstream side of the check valve body. Each of the injection hole and the passage of the swirl chamber at the upper direction and the lower direction have the same structure.
However, in the above stated direct fuel injection device, the check valve is arranged at a discharge side. Further, the elements which produce the swirl force are provided at a downstream side of a metering portion of the fuel passage, rather than at an upstream side of the metering portion of the fuel passage.
As a result, after the fuel passes through the metering portion of the fuel passage without having a swirl force imparted thereto, the fuel is subjected to a swirl force for the first time at the downstream side of the metering portion of the fuel passage, namely the swirl force is imparted first in the swirl chamber in response to the applied air.
Accordingly, in the direct fuel injection device structure disclosed in the above stated Japanese patent laid-open publication No. Hei-5 33,739, there is no suggestion to impart the swirl force to the fuel using a portion of the fuel passage upstream of the metering portion of the valve body.
In the conventional technique employed in the above stated direct fuel injection device, the atomization of the fuel is promoted and the spray direction of the fuel and the spreading of the fuel spray have been controlled. However, as stated hereinafter, full consideration has not been given to the shape of the fuel spray, the diameter of the fuel spray and the structure of the fuel spray in which both the ignitability (a spark-in property) and the combustibility (a propagation of fire) are improved in a compatible way.
To attain the optimum property for the spray of fuel which is injected from the fuel injector, it is necessary to consider at least the following three characteristics.
First of all, the first characteristic is the fuel spray shape, and the factors for this fuel spray shape are the spreading angle and the distance or extent of travel of the fuel spray. The second characteristic is the size of a spray fuel particle, in this regard, and it is necessary to lessen the number of spray fuel particles of large size as much as possible and to improve the uniformity of the spray fuel particle size distribution. The third characteristic is the structure of the fuel spray, and, for this purpose, it is necessary to provide a suitable spatial distribution of the fuel particles to be sprayed.
The inventors of the present invention have studied by experimentation various analyses as to how these fuel spray characteristics relate to the combustion properties in the internal combustion engine. As a result of these studies, they have found that, in a case where the spreading angle of the spray of the fuel is large, the inertia force of the fuel spray is weak, with a result that the distance or extent of travel of the fuel spray is short, whereby it is possible to obtain stability in the combustion. Further, on the other hand, by making the spreading angle of the spray of the fuel small, the inertia force of the fuel spray is made strong, with a result that a mixture of air and fuel having a superior ignitability is produced, but it was ascertained clearly that there is a tendency for unburned gas components (HC, CO) in the fuel to increase.
An object of the present invention is to provide a fuel injector which can inject a complex solid cone of fuel as a spray to provide a fuel spray having a superior combustibility in which the discharge amount of unburned gas components can be reduced and a fuel spray having improved ignitability can be provided for use in an internal combustion engine.
Another object of the present invention is to provide a fuel injector which can inject a spray in the form of complex solid cone of fuel particles to provide a fuel spray having a superior combustibility in which the discharge amount of unburned gas components can be reduced and a fuel spray having an improved ignitability can be provided for use in an internal combustion engine so as to obtain a superior ignitability of the internal combustion engine and to reduce the discharge amount of the unburned gas components in the fuel.
As to the spray formed as a complex solid cone of fuel particles in the fuel injector, it is desirable to form a fuel spray which comprises a first fuel spray having a large spreading angle by the inertia force thereof weak and the distance or extent of travel thereof short, and a second fuel spray having a small spreading angle by making the inertia force thereof strong.
In order to produce such a complex solid cone spray of fuel from a fuel injector, a fuel injector according to the present invention comprises a nozzle body having an injection hole, a valve body, and a drive means for driving the valve body in an axial direction, so that, by driving the valve body, the injection hole is opened and closed and the fuel injection is carried out.
In the fuel injector, at a side upstream of the injection hole, two swirl force producing means for imparting a swirl force to the fuel are arranged in the axial direction, the two swirl force producing means comprise a first swirl force producing means and a second swirl force producing means, whereby the swirl force imparted by the first swirl force producing means differs from the swirl force imparted by the second swirl force producing means, whereby a fuel injection in the form of a solid cone spray is carried out.
In a fuel injector according to the present invention, at a side upstream of the injection hole, two swirl force producing means for imparting a swirl force to the fuel are arranged to have a two stage form in the axial direction, the two swirl force producing means comprise an upstream side swirl force producing means and a downstream side swirl force producing means, with the upstream side swirl force producing means imparting a stronger swirl force to the fuel than the swirl force produced by the downstream side swirl force producing means, whereby a fuel injection in the form of a solid cone spray is carried out.
The fuel to which a strong swirl force is imparted forms a first fuel spray having a large spreading angle by weakening the inertia force and shortening the distance or extent of travel thereof. The fuel to which a weak swirl force is imparted forms a second fuel spray having the small spreading angle due to a strong inertia force. The complex solid cone fuel spray is formed by the first fuel spray and the second fuel spray.
In a fuel injector according to the present invention in which fuel having a swirl force imparted thereto is injected, from an injection hole, a preceding spray is injected to a central portion, and in succession to the preceding spray, another spray is injected radially to a surrounding portion of the preceding spray, whereby fuel injection having a solid cone spray is carried out.
In a fuel injector according to the present invention in which fuel having a swirl force imparted thereto is injected, a cross-section of the spray shape, including an axial center of the valve body of the fuel injector, produces a strong spray distributed in three directions, whereby fuel injection having a solid cone spray is carried out.
The fuel spray at the central portion attracts small diameter droplets, such small diameter droplets are injected continuously into the fuel at a surrounding portion of the fuel spray with a hollow shape spray and with a radial shape spray. As a result, a solid cone fuel spray structure having a superior dispersion property can be formed.
The fuel spray at the central portion is mainly a fuel spray made up of fuel to which is imparted a weak swirl force. The fuel spray which follows the above fuel spray and is injected with a radial shape is mainly a fuel spray made up of fuel to which is imparted a strong swirl force.
According to a high speed photograph of the fuel spray structure during fuel injection, it was observed that the fuel spray which is injected at the central portion reaches a remote location relative to the fuel spray which is sprayed at the surrounding portion a the radial shaped spray. A cross sectional view of the fuel spray structure will show the following characteristics.
Namely, in the fuel injector obtained according to the present invention, which injects fuel while imparting a swirl force to the fuel, the cross sectional view of the fuel spray structure, taken along the axial center of the fuel injection, shows a strong fuel spray extending in three directions.
A fuel injector according to the present invention comprises, at a side of an upstream of the injection hole, two swirl force producing means for imparting a swirl force to the fuel, which are arranged with a two stage form superimposed in the axial direction, the two swirl force producing means comprise an upstream side swirl force producing means and a downstream side swirl force producing means, and the upstream side swirl force producing means imparts a weaker swirl force to the fuel than a swirl force of the downstream side swirl force producing means, thereby a fuel injection with a solid cone spray is carried out.
In a fuel injector according to the present invention in which fuel is injected, while imparting a swirl force to the fuel, from an injection hole, a preceding spray is injected radially into an annular area, and in succession to the preceding spray, another spray is injected to a central portion of the annular area, thereby fuel injection with a solid cone spray is carried out.
A fuel injector according to the present invention comprises a nozzle body having an injection hole for injecting fuel and a seat face provided upstream of the injection hole, a valve body for opening and closing a fuel passage at the seat face of the nozzle body, at a side of an upstream of the seat face of the nozzle body, an element having a penetration hole in which the valve body extends, an axial direction fuel passage for passing fuel in an axial direction and a radial direction fuel passage communicating with the penetration hole from the axial direction passage for passing the fuel in a radial direction.
The radial direction fuel passage includes a first radial direction passage and a second radial passage superimposed in the axial direction, whereby an off-set amount of the first radial direction passage differs from an offset amount of the second radial direction passage, thereby fuel injection with a solid cone spray is carried out.
An off-set amount from an axial center of the valve body of one of the two radial direction passages, which is provided at a relatively remote position from the injection hole and communicates with the penetration hole at an upstream side thereof, is made the same or larger than an off-set amount of an opening of the other radial direction passage which is provided relatively near the injection hole, thereby fuel injection with a solid cone spray is carried out.
According to the above stated fuel injector, the flow direction of the fuel which passes through the radial direction passage remote from the injection hole is angled away from the axial center of the valve body as compared to the flow of the fuel which passes through the radial direction passage near to the injection hole. As a result, the fuel which has imparted the strong swirl force at the upstream side is injected continuously from the injection hole to the fuel which has imparted the weak swirl force at the downstream side. For reasons stated above, a complex solid cone fuel spray is formed.
A fuel injector according to the present invention comprises, an upstream of the seat face of the nozzle body, an element having a penetration hole in which the valve body extends, an axial direction fuel passage for passing fuel in an axial direction and a radial direction fuel passage communicating with the penetration hole from the axial direction fuel passage for passing the fuel in a radial direction.
The radial direction fuel passage includes two radial direction passages which are provided with a two stage form superimposed in the axial direction, an off-set amount from an axial center of the valve body of one of the two radial direction passages, which is provided at a position relatively remote from the injection hole in communication with the penetration hole at an upstream side thereof, is made smaller than an off-set amount of the other radial direction passage, which is provided relatively near the injection hole, thereby fuel injection with a solid cone spray is carried out.
An internal combustion engine having a fuel injector with the features described above, according to the present invention, comprises a cylinder, a piston which reciprocates in the cylinder, an air intake means for introducing air into the cylinder, a discharge means for discharging combustion gas from the cylinder, a fuel injector for directly injecting fuel into the cylinder, a fuel supply means for supplying fuel from a fuel tank to the fuel injector, and an ignition means for igniting a mixture of air and fuel which comprises air introduced in the cylinder by the air intake means and fuel injected into the cylinder by the fuel injector, the internal combustion engine.
The piston of the engine has a cavity portion at an upper face thereof and the cavity portion changes the direction of the spray which is injected from the fuel injector to deflect it to the ignition means.
According to the internal combustion engine obtained by the present invention, as stated in above, since a complex fuel spray is formed in the cylinder, a superior ignitability is achieved in the internal combustion engine and the combustibility in the internal combustion engine can be improved, as a result of which, the discharge amount of unburned gas components of the combustion can be reduced.
Since the fuel is injected toward the cavity portion which is constituted on the upper face of the piston, the fuel spray having a strong inertia force which has imparted a weak swirl force collides vigorously with the cavity portion and the direction of the fuel is changed to deflect it toward the ignition device (an ignition plug). Since the fuel which is changed in direction and has a strong inertia force attracts small diameter droplets at the surrounding portion to further promote fuel dispersion, the ignitability can be improved and the combustibility in the internal combustion engine can be improved further.